Balance with a weighing compartment

ABSTRACT

A balance ( 1 ) has a weighing compartment ( 4 ) that borders on a stationary part ( 8, 9 ) of the balance and is otherwise enclosed by at least one side wall panel ( 5, 6 ), a front wall panel ( 7 ), and a top cover panel ( 12 ). At least one of the side wall and top cover panels is slidable by means of a guiding device ( 17, 120 ) to open and close the weighing compartment ( 4 ). A holder arrangement ( 15, 17   c,    58, 125 ) for the at least one slidable panel ( 5, 6, 12 ) is integrated in the guiding device ( 17, 120 ), and a holder arrangement for a non-slidable panel is integrated in the stationary part ( 8 ). The holder arrangements ( 15, 19, 17   c,    58, 125 ) releasably connect the panels ( 5, 6, 7, 12 ) to the balance by means of form-locking closure devices, so that each panel ( 5, 6, 7, 12 ) can be attached to the balance as well as released for removal from the balance by applying a force to the panel ( 5, 6, 7, 12 ) and/or the holder arrangement ( 15, 19, 17   c,    58, 125 ).

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a balance with a weighingcompartment that borders on a stationary part of the balance and isotherwise enclosed by at least one side wall, a front wall, and a topcover panel, where at least one of the walls and/or the top cover panelis slidable by means of a guiding device to open and close the weighingcompartment.

[0002] A known balance of this kind, as described for example in theEuropean patent application EP-A-0 234 008, has a weighing pan and aweighing compartment that encloses the weighing pan on all sides, with astationary front glass wall, rearward-sliding side walls, arearward-sliding top cover panel, and a connector that joins the sidewalls with the top cover panel. The connector is configured so that whena side wall and/or the top cover panel is opened or closed, theconnector moves together with the side wall and/or the top cover panel,so that the weighing compartment is freely accessible without beingobstructed by frame members on the sides. Furthermore, the side wallscan be opened and closed individually or together, with or withoutmoving the top cover panel at the same time. The movement can bemotorized or manual. With manual operation, the walls that are to bemoved are uncoupled from the motorized drive mechanism.

[0003] The European patent application EP-A-0 574 668 discloses abalance that has a draft-protection housing with a top cover panel thatcan be attached or taken off by means of a manually operated lockingarrangement. After the top cover panel has been taken off, the frontwall as well as the side walls can be completely removed from thehousing for cleaning. In this known design of a balance, the top coverpanel is part of a frame that holds the draft-protection housingtogether. To a certain extent, the walls are unobstructed by the framemembers so that the operator has a better view of the interior of thehousing, but for some applications, this design is still not entirelysatisfactory. One drawback is that the upper part of the frame is stilla required element, and another concern is that the locking elements,which have to be manufactured with high precision, require a certainamount of manipulation in order to align them with the recesses in whichthey are received.

[0004] In state-of-the-art balances, if conduits, hoses, or otherconnections have to be introduced into the weighing compartment in aflexible, non-permanent arrangement, a slidable side wall or the topcover panel has to stay at least partially open during the weighingprocess, because the rigid frames and complicated guiding devices do notallow the walls to be provided with individual, easily accessibleconduit passages. However, leaving a wall open can cause errors in theweighing result.

[0005] In essence, known balances suffer from the drawback that theydon't simultaneously allow free, unrestricted access to the weighingcompartment as well as an unobstructed view of the weighing pan.Simultaneous access from the side and from above is not possible, aproblem that applies in particular to the accessibility for conduits,hoses or other connections. In addition, the weighing compartment isdifficult to clean.

OBJECT OF THE INVENTION

[0006] It is therefore the object of the present invention, to provide abalance with a weighing compartment that simultaneously offers anunobstructed view of the weighing pan and good accessibility in allsituations, and to accomplish this objective through a simple conceptthat also makes the manipulation easy for the user. The weighingcompartment should be conveniently accessible for placing a sample onthe pan when the walls are open, and it should allow the passage ofconduits and cables with the wall completely closed. In addition, itshould be easy to clean, without the need for complex manipulations.

SUMMARY OF THE INVENTION

[0007] The present invention offers a solution to the aforedescribedproblem in a balance with a weighing compartment that borders in part ona stationary part of the balance and is otherwise enclosed by at leastone side wall panel, a front wall panel, and a top cover panel panel,where at least one of the walls and/or the top cover panel is slidableby means of a guiding device to open and close the weighing compartment.According to the invention, a holder arrangement for the at least oneslidable wall panel is integrated in the guiding device, and a holderarrangement for each of the non-slidable wall panels is integrated inthe stationary part of the balance. Each wall panel is releasably heldin position by its respective holder, which can be locked and unlockedby engaging and disengaging a form-locking closure device that isoperated simply by applying a force to the wall panel and/or the holderarrangement.

[0008] The side walls, the front wall, and the top cover panel can beindividually separated by hand from the balance by simply pulling atthem lightly to tilt them outwards, e.g., for easy cleaning of the wallplates, which are normally made of glass. When they are in their workingposition, the walls are positively locked into place. The same handmovement is used to unlock each of the walls. Besides making theweighing compartment easy to disassemble for cleaning, the concept ofintegrating the holder arrangements of the slidable walls in the guidingdevices also accomplishes the objective of making the weighingcompartment freely accessible and of allowing an unobstructed view ofthe weighing pan even when the weighing compartment is closed, with nosight-blocking frame members being in the way.

[0009] It is advantageous if at least one of the holder arrangementscontains a snap-closure body for an automatic snap connection of therespective wall panel. Preferably, the snap-closure body is attached tothe rear wall of the weighing compartment and designed as a holder andguide for the side walls.

[0010] The concept of at least one snap-closure body to hold, e.g., theside walls in their operating position is particularly favorable for adesign without frame members. The kind of support frame that is requiredwith prior-art designs is not necessary in balances according to thepresent invention. A snap-closure body can be manually operable, so thata wall can be attached or released by, respectively, pushing or pullingat the wall. A snap-closure body is designed so that a larger amount offorce is required to pull off a wall panel than to snap it into place,so that the wall panel is held in place very securely. The special shapeof the snap-closure bodies and their design as a single-piece plasticarticle make them particularly cost-effective to produce.

[0011] To keep out air drafts that could enter at the joints between thewalls of the weighing compartment, a further embodiment of the inventivebalance has edge joints where the edge of one wall is seated in a grooveof the other, or one wall has an edge-cover strip to close off a gapthat could form at the joint between the two walls.

[0012] A preferred embodiment of the balance has a means for driving themovement of the at least one slidable wall panel. Preferably, the drivemeans are designed as cord-pulley drives.

[0013] The slidable walls are releasably attached to guiding deviceswith couplers or clutches by which the guiding device for eachindividual wall panel can be connected to or disconnected from the drivemeans. The couplers are provided with levers so that they can beoperated by hand. As a result, the side wall panels and/or the top-coverpanel can be driven either individually or together or in any desiredsub-combination. For example, it is possible to open and close only oneside wall, or only the top cover panel. Advantageously, the couplerarrangement includes traveling coupler elements that automatically seekand find the position for engagement. For example, if a side wall isuncoupled from the drive, pushing the coupler actuator on the side wallwill cause the latter to be coupled to the drive as soon as thetraveling coupler element of that side wall has reached its counterparton the wall panel.

[0014] In an advantageous embodiment of the invention, the drive meansare powered by only one motor.

[0015] According to a further embodiment of the invention, the traveldistance between the open and closed positions can be different for theside walls than for the top cover panel, in which case the movements ofthe respective drive means can be synchronized by using differenttransmission ratios corresponding to the different travel distances.Thus, the same motor can be used to drive the side walls and thetop-cover panel.

[0016] The balance is preferably equipped with a carrying handle. Thus,the balance can, e.g., be lifted from the table with one hand, whilecleaning the table surface underneath the balance with the other hand.As a special feature of the invention, the carrying handle serves at thesame time as a guide rail for the guide element of the top-cover panel,with a guiding device being arranged on the handle. In an advantageousembodiment, the guiding device has at least one gear rack in an upperarea of the guiding device and a parallel gear rack in a lower area. Avertical body of the guide element contains a pair of identical gearsfixed on a vertical axle and rolling along the gear racks, whereby theguide element is held in alignment and prevented from jamming as itmoves back and forth. This vertical arrangement of the guide element hasthe advantage that it minimizes the length of the guiding device for thetop cover panel.

[0017] In a particularly preferred embodiment of the balance accordingto the invention, passage openings are provided in the side walls, thefront wall, the top cover panel, and/or the rear wall of the weighingcompartment for conduits and cables. The passage openings can be closedoff against air drafts by means of clip-on covers. This concept has amultitude of possible applications where experiments are conductedinside the weighing compartment and weight changes are observed as partof the experiment, for example when reagents are dispensed into a beakeron the balance pan, or when a chemical reaction is being studied. Adesign without frame members along the edges and the possibility oftilting the walls outwards without removing them from the balanceprovides a simple way of running electrical supply and signal cables orconduits for fluids and gases through the cutout passages, to secure thecables and conduits in the cutout openings, and to seal the latteragainst air drafts by means of special clip-on holders. Specialconfigurations of the clip-on devices, e.g., as holder elements, expandthe range of their possible uses.

[0018] A special embodiment of the balance according to the inventionhas an accessory unit arranged, e.g., at the rear of the balance. Theaccessory unit contains power supplies and/or control units. Cablesconnected to this accessory unit through openings can be routed to thecutout passages through special guide channels along the housing, sothat they will not interfere with the movement of the side walls.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Further details of the invention may be learned from thefollowing description of embodiments that are illustrated in thedrawings, wherein

[0020]FIG. 1 represents a perspective frontal view of a balanceaccording to the invention;

[0021]FIG. 2a and 2 b represent sectional views of an edge portion ofthe weighing compartment in an area where two walls meet;

[0022]FIG. 3a to 3 c represent sectional views of the attachment of thefront wall of the weighing compartment in three different positions;

[0023]FIG. 4 illustrates a first alternative of the wall attachment in asectional view;

[0024]FIG. 5 illustrates a second alternative of the wall attachment ina sectional view;

[0025]FIG. 6 shows the weighing compartment as seen from a directionaccording to the arrow VI of FIG. 1;

[0026]FIG. 7 illustrates the detail VII of FIG. 6;

[0027]FIG. 8 illustrates the detail VIII of FIG. 6;

[0028]FIG. 9 illustrates the detail IX of FIG. 6;

[0029]FIG. 10 shows a balance in perspective as seen in the direction ofthe arrow II of FIG. 1, but with the housing removed;

[0030]FIG. 11 shows a sectional view of the lower portion of the balanceas seen from the front;

[0031]FIG. 12a to 12 d illustrate a coupler device for the side walls indifferent views;

[0032]FIG. 13 represents a sectional view of the guiding mechanism andthe drive mechanism of the top cover panel;

[0033]FIG. 14 represents a side view of the drive mechanism of the topcover panel;

[0034]FIG. 15 gives a schematic representation of the entire drivemechanism;

[0035]FIG. 16a and 16 b illustrate a concept for fastening the cord asseen from the side (FIG. 16a) and from the front (FIG. 16b);

[0036]FIG. 17 shows a possible use for the openings in the rear wall, asseen from the top;

[0037]FIG. 18 shows a possible use for the clip-on devices, as seen fromthe front;

[0038]FIG. 19 shows a possible use of the clip-on devices for anembodiment of the balance with wall panels of reduced height, in asectional view; and

[0039]FIG. 20 shows a balance seen at an oblique angle from the rearwith accessory unit, holder device and guide channels, in athree-dimensional representation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0040] A balance according to FIG. 1 has a stationary part with a floorcompartment 2 that contains a portion of the working system of thebalance, a housing 3 that essentially contains the drive mechanism, anda weighing compartment 4. The rear wall 9 and the floor 8 of theweighing compartment 4 are formed by the stationary part. The weighingcompartment 4, which serves as a draft shield, is further enclosed bythe side walls 5, 6, the front wall 7, and the top cover panel 12. Thefloor 8 has a pass-through opening for the carrier of the weighing pan10. However, the weighing pan can also be supported by an L-shapedcantilever arm that is attached to a coupling arrangement that passesthrough the rear wall of the weighing compartment, as described in theparallel patent application CH-1957/00. The different designs of theweighing pan and/or the features of the weighing compartment describedin the reference just mentioned are likewise applicable to the balancedescribed herein.

[0041] Preferably, the balance 1 stands on three feet 22.

[0042] The side walls 5, 6, the front wall 7, and the top cover panel 12consist of a transparent material, preferably glass. It is also possibleto use tempered glass, especially to make the balance safer forapplications in rough environments or to make the walls less delicate tohandle, so that they can, e.g., be washed in a machine.

[0043] The side walls 5, 6 and the top cover panel 12 are slidable bymeans of a drive mechanism, e.g., a pull-cord drive, to open and closethe weighing compartment. Each of the side walls 5, 6 and the top coverpanel 12 are releasably attached to a guiding device 17, 120 by means ofholders that are integrated in the guiding devices 17, 120. The frontwall 7 is likewise releasably attached with a holder element 19.

[0044] By tilting them slightly, the side walls 5, 6, the front wall 7,and the top cover panel 12 can easily be removed from their holders forcleaning.

[0045] In their opened position, the side walls 5, 6 as well as the topcover panel surround the housing 3. This is possible, because thehousing 3 is dimensioned smaller in width and height than the weighingcompartment 4.

[0046] The guiding devices 17, 120 of the side walls 5, 6 as well as ofthe top cover panel 12 have coupling elements (not shown in FIG. 1) bywhich the side walls 5, 6 and the top cover panel 12 are connected tothe pull cords of a drive mechanism. Each of the side walls 5, 6 has aseparate actuator handle 18 for the coupling element, as does the topcover panel 12 (not shown in FIG. 1). The function of the couplings andthe drive mechanism are described below. This makes it possible to openand close the side walls 5, 6 and the top cover panel 12 eitherindividually or in any combination of two, or all at the same time.

[0047] The balance 1 is equipped with a carrying handle 13 at the top ofthe housing 3. In addition to its carrying function, the handle 13 alsoserves as a guide track for opening and closing the top cover panel 12.A guide element 14 of the guiding device 120 runs along the guide track.The top cover panel 12 is attached to the guide element 14 through theholder 15. As described above, the holder 15 of the top cover panel 12is configured in such a way that the top cover panel 12 can be takenoff, e.g. for cleaning, by a simple tilting movement.

[0048] The top edges of the side walls 5, 6 are framed by inward-slantedborder pieces 11 that hold the top edges in place through snap-closureelements ((not shown in FIG. 1, see FIG. 6) and rest against the slantedcorner sections 23, 24 of the rear wall 9 and the front wall 7,respectively. The angled portions of the border pieces can overlapdifferently shaped top edges of the side walls 5, 6 and also of the topcover panel 12 in such a manner that they form a kind of baffle sealagainst the outside air, so as to block air drafts even more effectivelyfrom entering the weighing compartment 4 than do common types of draftshields. As a further advantageous feature, the border pieces 11 can bemade of a transparent material.

[0049] It is further useful to give the edges, e.g., the rear and frontedges of the side walls 5, 6 as well as the lateral and top edges of thefront wall 7, a special shape to further reduce the possibility of airdrafts entering the weighing compartment 4. This is achieved byproviding one of the two walls that meet at a right angle with a groove182 of rectangular cross-section in which the other wall is seated, asillustrated by the example shown in FIG. 2a for the edge 183 where thefront wall 7 meets the side wall 6. Alternatively, an angle-profilededge-covering piece 180 can embrace the edge of a wall over its entirelength and protrude beyond the thickness of the wall to which it isattached, so that in a closed condition of the weighing compartment, theedge-covering piece 180 closes off a gap 181 that could exist betweenthe two walls. The edge-covering piece can be made, e.g., of transparentplastic so as not to obstruct the view into the weighing compartment 4.FIG. 2b shows the same edge as FIG. 2a, but with the alternativeconfiguration of the edge of the weighing room 4. It is self-evidentthat in order to tilt one of the walls 5, 6, 12 out of its respectiveholder, it will first have to be opened slightly to retract it from thegroove or from the reach of the edge-covering piece.

[0050]FIGS. 3a-3 c illustrate how the front wall 7 is released from itsattachment to the floor compartment 2. Of course, the system that isused for attaching and removing the front wall 7 could also be appliedfor the side walls 5, 6 as well as for the top cover panel 12. As can beseen in FIG. 3c, a part of a holder element 19 is connected to thebottom edge of the front wall panel 7 (also see FIG. 1). This holderelement 19 has a fork-shaped recess 50 at its bottom portion. The top ofthe holder element 19 has a protruding nose 49 with an indentation 47behind it. The nose 49 is a fixed part of the holder element 19. Toinstall the front wall 7, the fork-shaped recess 50 is seated on a rod48 that is arranged at the wall of the floor compartment 2 (FIG. 3b).Next, the front wall 7 is pivoted counterclockwise about the rod 48 andbrought into the position shown in FIG. 3a. A leaf spring 45 with alatch lever 44 and a roller 46 are arranged at the underside of thefloor 8. When the front wall 7 is raised from the tilted position inFIG. 3b to the upright position of FIG. 3a, the slanted side of the nose49 meets the roller 46 so that the latch lever 44 is pushed up farenough to let the roller 46 get over the nose 49 and snap into theindentation 47, as shown in FIG. 3a. As a result, the front wall panel 7is held firmly in position by the engagement of the fastener parts 50,48 and simultaneously, at a distance from the latter, by the engagementof the fastener parts 47, 46. As demonstrated through the drawings andthe foregoing description, no special actuating device for tightening orreleasing a clamp hold is necessary to hold the front wall panel 7 (andlikewise the other panels 5, 6 and 12 of the weighing compartment 4) inplace. Thus, in the sense of the foregoing discussion, the illustratedholder element 19 as well as the holder elements described below providea firm attachment in the operating position without requiring actuationof a fastener.

[0051] The spring-clamp connection according to FIGS. 3a to 3 crepresents the preferred arrangement, primarily because it does notrequire a groove, which would be difficult to clean, and also becausethe attachment with the spaced-apart fastener pairs 50, 48 and 47, 46 isvery stable. Nevertheless, numerous variations are conceivable andpractically possible, as shown in FIGS. 4 and 5. For example, thearrangement of FIG. 4 uses a groove or channel 51 in the wall of thefloor compartment 2. One or both of the vertical flanks of the channel51 are profiled with recesses into which strip moldings 52 are insertedlengthwise. The strips 52 have lips 53 of a suitable elastic material,e.g., a polymer. The lips 53 are preferably oriented at a downwardangle, as shown in FIG. 4, although they could also be arranged abouthorizontally. The front wall panel 7 (or, in an analogous way, one ofthe side wall panels 5, 6 or the top cover panel 12) has a holderelement 19′. The lips 53 push against the flanks of the holder element19′ that project from the surface planes of the front wall panel 7.After the front wall panel 7 has been pushed into the channel 51, thelips 53 will snap into place behind the projecting flanks. The amount ofresistance that the lips 53 will offer when the front wall panel 7 ispulled out of the channel 51 can easily be controlled in the designthrough the angle and dimensions of the lips which determine the amountof friction that will have to be overcome.

[0052] The channel groove 51′ in FIG. 5 has a flank 54 that is inclinedat an angle. After the front wall panel 7 has been set in place in thechannel 51′, one or more tightening rollers 55 are placed between thefront wall panel 7 and the inclined flank 54, in order to push the frontwall panel 7 firmly against a support surface 56. The stability of thisconnection depends on the height of the support surface 56 on one sideand the height of the position of the roller 55 from the bottom of thechannel 51′.

[0053] Although each of the aforementioned arrangements for attachingthe front wall panel 7 could also be used for the side wall panels 5, 6,an arrangement as illustrated in FIGS. 6 to 9 has the advantage that thewall panel can slide by means of its respective guiding device 17 (seeFIG. 1) while being clamped firmly in its working position.

[0054]FIG. 6 shows a frontal view of the balance 1, looking at the rearwall 9 of the weighing compartment. The left side wall panel 5 is shownin a released condition, while the right side wall panel 6 is in aninstalled condition and connected to the guiding device 17. The guidingdevice 17 has a guide channel 17 a and a supporting surface 17 b.

[0055] As shown in FIG. 7 (magnified view of detail portion VII of FIG.6) and FIG. 8 (magnified view of detail portion VIII of FIG. 6), theguiding device 17 at the front and rear ends (in relation to the viewingdirection of FIG. 6) has outward projections 17 d containing cylindricalpivot pins 17 c. The pivot pin 17 c leaves enough room behind it so thata hook-shaped hinge part 58 can be engaged by the pivot pin 17 c. Thehinge part 58 is a component of a border strip 57 that is attached tothe side wall panel 5. An analogous arrangement is used for the sidewall panel 6. FIG. 7 shows a cross-section through the mid-portion ofthe border strip 57, where the latter has hook-shaped hinge parts 58 atboth ends that match the locations of the aforementioned projections 17d with the pivot pins 17 c. FIG. 8 illustrates a cross-section throughan end portion of the border strip 57 with one of the hook-shaped hingeparts 58 engaging a pivot pin 17 c.

[0056] In contrast to the design concept of FIG. 3 with two fastenerpairs 50, 48 and 47, 46 at the underside of the weighing room floor 8,the holder arrangements for the side wall panels of FIGS. 6 to 9 haveone of the two fastener pairs located at the top of the wall panel,either on the forward-facing side of the rear wall 9, as shown in FIG.6, or on the rearward-facing side.

[0057] The second fastener pair (detail portion IX of FIG. 6, magnifiedin FIG. 9) uses a snap-closure device 125 of a special design with aframe-like snap-closure body 59, preferably an integral injection-moldedpolymer part. The snap-closure body 59 consists of an approximatelyvertical supporting portion 60 from which a tongue 61 extends in anapproximately horizontal direction. The tongue 61 has a fulcrum hole 62where the snap-closure body is rotatably supported. However, the rangeof rotation is limited by a bolt 64 that is mounted in the rear wall 9and restrains the tongue 61. A spring member 63 extends out of thetongue 61, about parallel to the latter, and is tension-biased againstthe bolt 64. As the spring member 63 is relatively stiff, it resists aclockwise rotation of the snap-closure body 59. In addition to thetongue 61, two parallel, elastically flexing arms 68 also projecthorizontally from the supporting portion 60, connected at their oppositeends by a vertical leg 67. The ends of the horizontal arms 68 near thesupporting portion 60 and the vertical leg 67 are thinner and longerthan the flexing portion of the spring member 63 near the tongue 61, sothat the pair of horizontal elastic arms 68 preferably offer a weakerspring force than the spring member 63.

[0058] The vertical leg 67 extends upwards into a post 69 with slopedtop 70. The sloped top 70 cooperates with an opposing sloped surface 71of a border piece 11 which is attached to the top of a side wall panel5, 6 (see FIG. 1 and 6) and which is preferably made of a transparentmaterial. When the side wall panel 5, 6 is set in place with its hingeparts 58 on the pivot pins 17 c, as shown on the left of FIG. 6 (and inthe magnified detail VII in FIG. 7), and then pivoted into the uprightclosed position, as shown on the right of FIG. 6, the opposing slopedsurface 71 glides on the sloped top 70 of the post 69 and thereby exertsa force against the snap-closure body 59. The horizontal force componentacting against the body 59 is absorbed by the rear wall 9. The verticalforce component causes a downward deflection of the flexible arms 68with the vertical leg 67 and post 69 until the opposing sloped surface71 has cleared the sloped top 70 and the post 69 snaps into the groove72 behind the opposing sloped surface 71. This represents the engagedcondition of the snap-closure device 125, as illustrated in FIG. 9.

[0059] While the snap engagement of the post 69 in the groove 72 behindthe opposing sloped surface 71 requires only a relatively small effortdue to the soft spring characteristic of the arms 68, a comparativelygreater effort is required to disengage the snap closure. When the sidewall panel 6 is pulled clockwise with respect to its hinge 17 c, 58 fromthe vertical position shown in the right-hand part of FIG. 6, the leftvertical flank of the groove 72 pushes against the post 69. As thehorizontal pushing force runs eccentric to the fulcrum hole 62, itexerts a torque on the snap-closure body 59. However, because thehorizontal pushing force has a short lever arm, a relatively large forcewill be required to cause the body 59 to rotate clockwise about thefulcrum 62, with an additional amount of resistance being contributed bythe spring member 63. When the torque acting on the snap-closure bodyhas become large enough, the snap-closure body 59 turns counterclockwiseabout the fulcrum hole 62 against the force of the spring 63 until thepost 69, which is constrained to a translatory movement, has left thegroove 72 and the side wall panel 5, 6 is thereby released. An abutmentsurface 65 of the snap-closure body 59 above the fulcrum hole 62 restsagainst the upper edge of the rear wall 9 and thereby reduces thetendency of the spring member 63 to overshoot in the opposite directionafter the release of the side wall. Of course, one could use any otherforce-generating device instead of the spring 63, e.g., a magneticelement. However, the arrangement with the spring member 63 is preferredbecause its integration into the snap-closure body, particularly in aninjection-molding process, offers a cost advantage in production.

[0060] The advantages of this arrangement are that it requires lesseffort for putting a wall panel back in place than it takes forreleasing it, and that the movement of the side wall 5, 6 by means ofthe guiding device 17 is securely guided by the engagement of the post69 in the groove 72. It is self-evident that the references to “right”,“left”, “top”, “bottom” are meant in a relative sense. For example, thetwo snap-closure bodies 59 in FIG. 6 are mirror-symmetric so that leftand right are switched from one to the other. It also goes withoutsaying that a snap-closure body 59 could be assembled from a pluralityof components, although the concept of an integral injection-molded partis favored from a manufacturing point of view. One could also do withoutthe parallel-guiding arrangement of the leg 67 by means of the twoflexing arms 68 and use a single flexure arm instead, in which case thepost 69 would, however, need more horizontal clearance in the groove 72so that the movement of the post 69 in the groove 72 would not be guidedwith the same precision. Further possibilities are to connect the postat any other location on the leg 67 or a flexure arm 68, or to have oneor more posts connected to the sliding wall panel and a groove on astationary part, so that the relationship between the parts 69 and 72would be reversed.

[0061]FIG. 10 illustrates a balance 1 as seen in the direction of thearrow II of FIG. 1, with the housing 3 partially removed and theweighing compartment 4 closed. The side walls 5, 6 as well as the topcover panel 12 can be moved individually or together, either manually orin a motorized mode, preferably with a single motor 28, so that eitheror both sides and/or the top of the weighing compartment can be openedand closed as desired in a given situation. FIG. 10 illustrates inparticular the drive mechanism for moving the panels 5, 6 and 12, whichextends on the three levels 25, 26, 27 and a further level 36. Thedrive-mechanism shown in this example is a cord-pulley drive (describedin detail in the context of FIG. 15). An upper cord-pulley drive on thelevel 26 (not visible) serves to move the top cover panel, and a lowercord-pulley drive on the level 36 (likewise not visible) serves to movethe side walls 5, 6.

[0062]FIG. 10 further shows the guiding mechanism for the top coverpanel 12. The carrying handle 13 simultaneously serves as a guide railfor the guide element 14 of the holder 15 of the top cover panel 12,which runs along the carrying handle 13. The handle 13 is connected tothe level 26 though a connector brace 34. Two holding members 32 for thehousing 3 (removed in FIG. 10) are arranged between the connector brace34 and the rear wall 9. A lower portion 33 of the guide element 14 isarranged below the holding members 32 and joined through a narrowconnector 41 to the holder 15 of the top cover panel 12 (The designdetails are illustrated in FIG. 13).

[0063] The cord-coupling lever 16, serves to couple and uncouple the topcover panel 12 with the upper cord-pulley drive 38 (see FIG. 14)

[0064]FIG. 11 shows a sectional view of the floor compartment 2 of thebalance 1. The reference symbol 42 stands for the operative weighingportion of the balance, to which the weighing pan 10 is connected in aknown manner. As mentioned above, the operative weighing portion 42 canalso be arranged in the housing 3 in a different configuration of thebalance, and the weighing pan can be coupled to it by means of anL-shaped support.

[0065] On either side of the operative weighing portion 42, a guideelement 43 extends over the entire length of the balance 1 as astationary component connected to the floor compartment 2. At its upperoutside edge, the guide element 43 has a rectangular projection 150 thatis engaged in the guide channel 17 a of the guiding device 17(illustrated in the left-hand portion of FIG. 11).

[0066] Another guide channel 151 which, however, extends over only apart of the length of the guide element 43, is arranged at the bottom ofthe guide element 43. The channel 151 is engaged by a guide bolt 40which is connected to the guiding device 17 by means of a bolt bracket40 a. The position of the guide bolt 40 and the position and length ofthe guide channel 151 in relation to each other are coordinated so as toform end stops for the travel of the bolt 40 in the guide channel 151.Other recesses and hollow spaces of the guide element 43 are providedfor the cord of the lower cord-pulley drive 39 that serves to move theside walls 5 and 6.

[0067] The guiding devices 17 of the side walls 5, 6 can be coupled toor uncoupled from the cord-pulley drive 39 through detent-lockingside-wall couplers 119 (shown in the right-hand portion of FIG. 11, andalso in FIG. 12) that are operated by means of coupling actuators 18.The lever 18 has two detent positions 156 for a spring element 155. Theside wall is coupled to the cord-pulley drive when the lever 18 is inthe upright position. When the lever 18 is pushed into the inclinedposition, the spring element 155 engages the lower of the detents 156and pushes the rod 152 against the angled lever element 153 and causesthe latter to tilt about the pivot axle 157 and lift the coupler spring154 out of the traveling coupler element 106. This is illustrated indetail in FIGS. 12a to 12 d, where FIG. 12a shows the traveling couplerelement 106 in a perspective view; FIG. 12b shows the coupler elementwith the angled lever element 153 and the coupler spring 154 in a topview; and FIGS. 12c and 12 d show a side view of the couplingarrangement in the engaged position (FIG. 12c) and the disengagedposition (FIG. 12d).

[0068] The traveling coupler element 106, which is fixedly connected tothe cord-pulley drive 39 and holds the cord in a groove 158, has ramps107 and 107′ rising from the ends towards the center of the couplerelement. When the coupling lever 18 is in the engaged position and thetraveling coupler element 106 happens to be at a different locationalong its travel range, the traveling coupler element 106 will during amovement of the cord-pulley drive automatically connect with the couplerspring as the tongue 159 of the coupler spring 154 will first be pushedup by one of the ramps 107 or 107′ and then snap into the notch 108between the ramps. Having been coupled to the cord-pulley drive, therespective side wall 107, 107′ is automatically moved to the desiredposition. In their uncoupled condition, the side walls 5, 6 can also bemoved manually. The coupler element 106 has a groove channel 141 thatruns along a guide rail of the guiding device 17.

[0069] The sectional view of FIG. 13 illustrates the guiding device 120of the top cover panel 12 (the latter not being shown in FIG. 13). Thebody 78 of the guide element 14 has laterally projecting ridges 79, towhich the plates 77 are attached by screws 80. The top portions ofplates 77 (broken off in FIG. 13) are connected to the holderarrangement 15 (likewise not shown) for the top cover panel 12. Theupper portion of the body 78 is surrounded by the carrying handle 13.Inside the carrying handle and to the left of the middle is an uppergear rack 73 which is engaged by an upper gear 73 a. A similararrangement is used with the lower gear rack 74 and the lower gear 74 ain the bottom portion 33 of the guide element 14. The gears 73 a and 74a are connected by a vertical shaft 66. To prevent any loose play fromside to side, there are pairs of guide rollers 75 and 76 arranged nextto the upper gear 73 a and the lower gear 74 a, respectively, so thatthe guide element 14 will always run straight and in correct alignmentalong the carrier handle 13. The vertical force on the guide element 14is taken up by a glide element 124. However, the guide element 14 couldalso run on one or more rollers. The underside of the bottom portion 33of the guide element 14 is coupled to the upper cord-pulley drive 38 bymeans of an arrangement that is shown in FIG. 16. The body 78 is movedalong the gear racks 73 and 74 by means of the cord-pulley drive 38. Thenarrow connector portion 41 of the body 78 runs in a slot 81 between theborder members 32 of the housing 3 (also see FIG. 10). The slot 81 canbe sealed against dust by overlapping lamellae, sealing lips or brushes.

[0070]FIG. 14 shows a side view of the drive mechanism for the top coverpanel 12, complementing FIGS. 10 and 13. The area of the drive source isarranged on two levels 25 and 26, as in FIG. 10, but without showing themotor 28 in the drawing. A coupling lever 16 is arranged at the rearwardend of the carrying handle 13, controlling a clutch 118 (not shown) thatcouples and uncouples a connection between the gear 82 and the pulley29, so that the top cover panel can be selectively coupled to oruncoupled from the motor 28. The motor 28 can be a reversible motor, ora reversing gearbox can be provided to allow the cord-pulley drive torun forward and backward. A gearbox could be either manually reversibleor actuators could be provided that work like electrical limit switchesto reverse direction when the guide element 14 reaches an end position.The drive power is transmitted from the motor 28 by way of a spur beltto the gear 30 which, in turn, drives the gear 82 through the pinion 89.

[0071] As may be seen in the drawing, the level 26 is formed by ahorizontal plate resting on tall columns 83, and the level 25 is formedby a smaller plate supported on the level 26 by short columns 84. Thelower gear rack 74, shown schematically in the drawing, can likewise besupported by the level 26 through columns 85 (only one of which isvisible in the drawing). The lower gear rack 75, the upper gear rack 73(arranged inside the carrier handle 13, as shown in FIG. 13), theconnector brace 34, and the rear wall 9 together constitute a rigidframe that hold the slidable top cover panel 12 in precise alignment.The top cover panel 12 is attached to the holder 15 which, in turn, isconnected by way of the plates 77 to the body 78 (not visible in thedrawing) of the guide element 14 as described above in the context ofFIG. 10. The lower portion 33 of the guide element 14 is guided alongthe lower gear rack 74. A pin-like connector element 86 protrudes fromthe underside of the guide element 14 and serves to connect the guideelement 14 to the upper cord-pulley drive 38. The cord is guided by thepulleys 29, 87 and 88 and is looped around the driving pulley 29 in aknown manner. The driving pulley 29 can run, e.g., on a ball bearing 90.

[0072] The gear 30 that is driven by the motor 28 by way of a spur belt(see FIG. 10) is connected through the shaft 35 to the pinion gear 89(shown in FIG. 14). The shaft 35 is configured in such a way that it canbe inserted and removed in a simple manner from above for assembly anddisassembly. The pinion gear 89 meshes with a gear 82 on a shaft 91whose position can be raised and lowered. By changing the verticalposition of the shaft 91 together with the gear 82, the latter iscoupled to and uncoupled from the pulley 29. The clutch between the gear82 and the pulley 29 can be designed in a variety of knownconfigurations, but an arrangement of ramps 92 with a locking springelement analogous to the concept of FIG. 12 is preferred. As the clutchis located in the narrow space between the pulley 29 and the gear 89,the positioning detent for the clutch spring is formed by two bolts withsloped upper end surfaces.

[0073] The top panel clutch 118 is operated by the clutch lever 16 thatwas already mentioned in the context of FIG. 10. By means of the lever16, the operator can selectively disengage the pulley 29 from themotorized drive 28, 82 in order to be able to manually move the topcover panel 12, or to move the side walls 5, 6 alone without moving thetop cover panel. The clutch lever 16 is connected to a cam disk 93 thatrotates together with the lever 16 on an axle 94 that is held by theconnector brace 34. A push rod 95 is guided for vertical movement insidethe connector brace 34. The two-armed lever 97 pushes the rod 95 upwardagainst the cam 93.

[0074] The other end of the two-armed lever 97 bears against the bottomend of the shaft 91 on which the gear 82 is mounted. A spring 98 that isattached to the level 25 bears against the top end of the shaft 91 andurges the latter downward against one arm of the lever 97. This causesthe lever arm on the other side of the fulcrum 96 to push the rodupwards against the cam 93. Thus, when the clutch lever 16 is movedcounterclockwise, the cam 93 pushes the rod 95 downward against theforce of the spring 98 and tips the two-armed lever 97 in the clockwisedirection. This causes the other lever arm to raise the shaft 91 withthe gear 82 and thereby disengage the clutch between the gear 82 and thepulley 29. In the disengaged position, the gear 82 stays in mesh withthe pinion 89. The manual actuation of the clutch could, of course, bereplaced by an automatic actuation, e.g., through an electromagneticactuating member.

[0075]FIG. 15 illustrates the overall drive mechanism with an uppercord-pulley drive 38 and a lower cord-pulley drive 39, without showingthe motor 28 and the gear 30 for the spur belt (see FIG. 10). The gear89 is connected to the drive shaft 35 that runs in bearings 102, 103 andtransmits the driving movement to the lower cord-pulley drive 39. Thecord of the upper drive 38 is looped in a full circle around the drivingpulley 29, then runs around the pulleys 87, 88, and returns to thedriving pulley 29, as shown in the drawing. The straight runs of thecord between the pulleys 87 and 88 are connected to the bottom portionof the guide element 14 of the guiding device for the top cover panel(see FIG. 14). The connection is made by means of a fastener element 86at a suitable location. A preferred design of the fastener element 86 isillustrated in FIG. 16 and will be described below.

[0076] A pinion gear 104 at the bottom end of the shaft 35 drives thelower cord-pulley drive 39 by way of the gear 99, which is in fixedconnection with the pulley 105. Analogous to the upper cord-pulley drive38, the cord of the cord-pulley drive 39 is looped in a full circlearound the driving pulley 105, then runs around the pulleys 100, 101 andreturns to the driving pulley 105, as shown in the drawing. The upperstraight runs of the cord between the pulleys 100 and 101 are connectedto the traveling coupler elements 106 for moving the side walls 5, 6(also see FIG. 12a-12 d).

[0077] As previously mentioned, FIG. 16 illustrates a possible way ofattaching the cord, as seen from the side in FIG. 16a and from the frontin FIG. 16b. The attachment device consists of a body 117 with a slot111 to receive the cord 38. The upper portion of the body 117 containsan internal thread. A sleeve 110 is set over the body 117 and a screw116 is turned far enough into the thread so that the sleeve clamps downon the cord.

[0078] As mentioned previously, the side walls 5, 6 and the top coverpanel 12 are slidable by means of a single motor 28. It is conceivablethat in some configurations of a balance, the walls 5, 6, 12 may havedifferent lengths of travel between their respective open and closedpositions. For example, the top cover panel 12 could move a longer orshorter distance than the side walls 5, 6. The configuration of thedrive system with cord-pulley drives 38, 39 as well as the connection tothe motor through a plurality of gears provides the design flexibilityto easily adapt the respective transmission ratios so that the walls 5,6 and the top cover panel 12 will move synchronously when they arecoupled to the drive.

[0079] It can further be of advantage if the drive mechanism is designedto recognize a desired direction of movement of the side walls 5, 6 andtop cover panel 12 when the operator manually pushes in the desireddirection against a suitable place on the respective side wall 5, 6 ortop cover panel 12. For example, if the clutch actuators 18, 16 arepushed or pulled while they are in their engaged condition, thedirection of movement could be detected by a sensor, and the motor couldbe activated to run in the desired direction. It is further conceivablethat the walls 5, 6 and top cover panel 12 are set in motion by pushingthem with a force that exceeds a threshold force, analogous to the way aCD-ROM drawer closes in response to a pushing force.

[0080] As illustrated already in FIG. 1, the rear wall 9 of the weighingcompartment is wider as well as taller than the housing 3. This makes itpossible to provide cutout openings 20 in the rear wall (see FIG. 1)that can be arranged on the sides as well as on top. The cutout openings20 can be closed by means of interchangeable clip-on covers 21. Forexample, the clip-on covers could be removed from one or more of thecutout openings 20 in order to provide passages for supply lines such aselectrical cables and/or hoses for liquids that are to be weighed. Inthis way, experiments can be performed inside the weighing compartmentwhile simultaneously observing weight changes without having to open theweighing compartment and thereby running the risk of causing weighingerrors. Of course, cutout openings 20 could conceivably be provided alsoin the side walls 5 or 6 and/or in the top cover panel 12.

[0081]FIG. 17 illustrates a possible use for the cutout openings 20 inthe rear wall 9 as seen from the top. While the cutout openings areusually closed off by clip-on covers to keep out air drafts, the clip-oncovers can be removed so that the openings can be used as passages forconduits, hoses, etc. FIG. 17 shows an example where a liquid isdispensed from the container 121 through the conduit 123 by way of thecutout opening 20 to the container 122 for weighing. Instead of leavingthe cutout 20 entirely open, it is advantageous to use a specialU-shaped clip-on device 21′ (see detail A) to better hold the conduit inplace.

[0082] As a further use for clip-on devices inserted into the cutoutopenings 20, FIG. 18 shows an example of a clip-on device 21″ with anequipment holder 130 that extends into the interior of the weighingcompartment 4. Equipment holders 130 that are installed in this mannercan be used for the flexible and removable arrangement of conduits,hoses, a thermometer 131 and/or all kinds of tools that are needed forexperimenting inside the weighing compartment 4.

[0083] A further application for the cutout openings is shown in FIG.19. It is conceivable to use versions or configurations of the balancewhere the side walls 114 are of a different height. In order to move thedifferent side wall panels 114 with the drive mechanism according to theinvention, a guide needs to be provided in the upper portion of the wallpanel 114. This can be accomplished by using suitable clip-on devices113 that are inserted into the cutout openings 20. Connected to the wallpanels 114 are holder rails 115 that are slidably guided by the clip-ondevices 113. Of course, removing the panels 114 from the balance is anequally simple procedure as described above for the wall panels 5, 6.

[0084] As shown in FIG. 20, an accessory unit 140 can be releasablyattached to the rear of the balance with a simple fastener, e.g., ascrew with a knurled head. The accessory unit 140 can containpower-supply units such as a battery, or an electronic control module.The accessory unit 140 has openings 147 for different kinds ofconnectors. This allows experimental setups, e.g., dispensing devices,in the weighing compartment 4 to be electrically connected to theaccessory unit 140. The cables and conduits enter the weighingcompartment 4 through the cutout openings 20, which are equipped withspecial clip-on holders comparable to the clip-on device 21′. To preventthe electrical cables and/or conduits, such as the conduit 123 in FIG.17, from interfering with the movement of the side walls 5, 6 as thelatter slide back along the housing 3, the rear wall 9 has recesses 142for the attachment of guide channels 143 on both sides of the housing 3.The guide channels are further held in place by slots 148 of a holderdevice 144 of the accessory unit 140. The guide channels 143 can forexample be made of metal or of a polymer material. As illustrated inFIG. 20, the guide channels can be designed in different ways; forexample, the guide channel 143′ is covered on top, so that it has theshape of a tube. It is also conceivable to design the guide channels asside-mounted modules attached to the housing 3 and extending over one ormore of the cutout openings 20. A further possibility is to arrange asimple electronic module or part of a module in the guide channels,particularly in an embodiment without the accessory unit 140.

[0085] The guide channels 143 can be no wider that is compatible withthe free movement of the side walls 5, 6. The ends of the guide channels143 are configured as connectors 145, 146 to attach the guide channelsto the rear wall and to the holder device 144, respectively. Theadvantage of this concept is that the weighing compartment 4 can be keptclosed to the outside, while experimental setups inside the weighingcompartment 4 of the kind that are described in detail, e.g., in theaforementioned patent application CH-1957/00 can still be supplied andoperated.

[0086] Of course, the housing 3, which is in essence occupied by thedrive mechanism, and the accessory unit 140 could be combined in acommon housing. The guide channels 143 for conduits and cables could beintegrated in the side walls of the common housing and they could alsobe closed to the outside with special covers. LIST OF REFERENCE SYMBOLS1 balance 2 floor compartment 3 housing 4 weighing compartment 5 sidewall panel 6 side wall panel 7 front wall panel 8 floor 9 rear wall 10weighing pan 11 border piece 12 top cover panel 13 carrying handle 14guide element 15 holder element for top cover panel 16 coupler lever 17guiding device 17a guide groove 17b support surface 17c pivot pin 17dprojection 18 clutch actuator 19, 19′ holder for front wall panel 20cutout passages 21, 21′, 21″ clip-on devices 22 feet 23, 24 slantedcorner sections 25, 26, 27 levels 28 motor 29 pulley 30 spur-belt gear32 holding member 33 bottom portion 34 connector brace 35 rotary shaft36 level 38 upper cord-pulley drive 39 lower cord-pulley drive 40 guidebolt 40a bolt bracket 41 connector portion 42 operative weighing portion43 guide element 44 latch lever 45 leaf spring 46 roller 47 indentation48 rod 49 nose 50 fork-shaped recess 51, 51′ channel 52 strip molding 53lip 54 inclined flank 55 roller 56 support surface 57 border strip 58hinge part 59 snap-closure body 60 supporting portion 61 tongue 62fulcrum hole 63 spring member 64 bolt 65 abutment surface 66 verticalgear shaft 67 vertical leg 68 flexible arm 69 post 70 sloped top 71opposing sloped surface 72 groove 73 upper gear rack 73a upper gear 74lower gear rack 74a lower gear 75 upper guide rollers 76 lower guiderollers 77 plates 78 body of guide element 79 ridges 80 screws 81 slot82 gear 83 tall columns 84 short columns 85 columns 86 fastener element87 pulley 88 pulley 89 pinion gear 90 ball bearing 91 shaft 92 ramparrangement 93 cam disk 94 axle 95 push rod 96 fulcrum 97 two-armedlever 98 spring 99 gear 100 pulley 101 pulley 102 bearing 103 bearing105 pulley 106 traveling coupler element 107, 107′ ramps 108 notch 110sleeve 111 slot 113 clip-on device 114 side wall panel 115 holder rail116 screw 117 body of attachment device 118 clutch for top cover panel119 side wall coupler 120 guiding device 121 container 122 weighingcontainer 123 conduit 124 glide element 125 snap-closure device 130equipment holder 131 thermometer 140 accessory unit 141 groove channel142 recesses 143, 143′ guide channels 144 holder device 145 connector146 connector 147 openings in the accessory unit 148 slots 150projection 151 guide channel 152 rod 153 angled lever element 154coupler spring 155 spring element 156 detent positions 157 pivot axle158 groove 159 tongue 180 edge-covering piece 181 gap 182 groove 183edge

What is claimed is:
 1. A balance (1) comprising a weighing compartment(4) that borders on a stationary part (8, 9) of the balance and isotherwise enclosed by at least one side wall panel (5, 6), a front wallpanel (7), and a top cover panel (12); wherein at least one of saidpanels is slidable by means of a guiding device (17, 120) to open andclose the weighing compartment (4); wherein further a holder arrangement(15, 17 c, 58, 125) for the at least one slidable panel (5, 6, 12) isintegrated in the guiding device (17, 120), a holder arrangement for anon-slidable wall panel is integrated in the stationary part (8), andthe holder arrangements (15, 19, 17 c, 58, 125) releasably connect thepanels (5, 6, 7, 12) to the balance by means of form-locking closuredevices, so that each panel (5, 6, 7, 12) can be attached to the balanceas well as released for removal from the balance by applying a force toat least one of said panel (5, 6, 7, 12) and said holder arrangement(15,19, 17 c, 58, 125).
 2. The balance of claim 1, wherein the front wallpanel (7) is non-slidable, the side-wall panels (5, 6) and the top-coverpanel (12) are slidable, and each of the panels (5, 6, 7, 12) can beindividually attached as well as individually released by hand.
 3. Thebalance of claim 1, wherein at least one of the holder arrangementscomprises at least one snap-closure body (59).
 4. The balance of claim3, wherein the stationary part (8, 9) comprises a rear wall (9), andwherein the at least one snap-closure body (59) is arranged on saidrear-wall (9) and serves to attach and release said at least oneslidable side-wall panel (5, 6).
 5. The balance of claim 3, wherein theat least one snap-closure body (59) comprises a vertical supportingportion (60), a tongue (61) protruding substantially horizontally fromthe vertical supporting portion (60) and containing a fulcrum hole (62)on which the snap-closure body (59) is rotatable, a spring member (63),and two parallel elastically flexible arms (68) connected by a leg (67),and wherein the spring member (63) is elastically biased against a bolt(64) of the rear wall (9).
 6. The balance of claim 3, wherein thesnap-closure body (59) is manufactured as a single integral piece ofpolymer material.
 7. The balance of claim 4 wherein the at least oneside wall panel (5, 6) is released from the snap-closure body (59)manually by pulling said side wall (5, 6) outwards in a tiltingmovement.
 8. The balance of claim 7, wherein the at least one side wallpanel (5, 6) is connected to the snap-closure body (59) by pushing saidside wall (5, 6) inwards and wherein the releasing the side wall panel(5, 6) from the snap-closure body takes a greater amount of force thanconnecting the side wall panel to the snap closure body.
 9. The balanceof claim 1, wherein the weighing compartment (4) has joints where anytwo of the panels (5, 6, 7, 12) meet each other and where the side wallpanels (6, 7) and top cover panel (12) meet the rear wall (9), andwherein at least one of said joints is formed by an edge of one beingseated in a groove of the other of said panels and rear wall, in orderto stop air drafts.
 10. The balance of claim 1, wherein the weighingcompartment (4) has joints where any two of the panels (5, 6, 7, 12)meet each other and where the side wall panels (6, 7) and top coverpanel (12) meet the rear wall (9), and wherein at least one of saidjoints is formed by an edge-cover strip attached to the edge of one andreaching around an edge of the other of said panels and rear wall, inorder to stop air drafts.
 11. The balance of claim 1, further comprisingdrive means (38, 39) for moving the at least one slidable panel (5, 6,12).
 12. The balance of claim 11, wherein the drive means comprisecord-pulley drives.
 13. The balance of claim 12, wherein the cord-pulleydrives comprise a first cord-pulley drive (38) arranged in an upper areaof the balance and a second cord-pulley drive (39) in a lower area ofthe balance, and wherein the cord-pulley drives (38, 39) are coupled toeach other by a common rotary shaft (35).
 14. The balance of claim 11,further comprising coupler devices (118, 119) by which the at least oneslidable panel (5, 6, 12) can be coupled to and uncoupled from the drivemeans (38, 39).
 15. The balance of claim 14, further comprising couplerlevers (16, 18) for manually actuating the coupler devices (118, 119).16. The balance of claim 14, wherein the couplers (119) comprisetraveling coupler elements (106) that automatically position themselvesfor engagement.
 17. The balance of claim 16, wherein the travelingcoupler elements (106) have ramps (107, 107′) rising towards each otherand separated by a notch (108), and wherein the balance comprises acoupler spring (154) connected to the at least one slidable panel (5, 6)and arranged so that the movement of the traveling coupler element (106)causes the coupler spring to slide up the ramp (107, 107′) and snap intothe notch (108), thereby coupling the slidable panel (5, 6) to thesecond cord-pulley drive (39).
 18. The balance of claim 11, wherein theside wall panels (5, 6) and the top-cover panel (12) are slidable,wherein the side wall panels (5, 6) have travel distances between theiropen an closed positions different from the top-cover panel (12), andwherein the drive means (38, 39) have transmission ratios adapted tosaid different travel distances, so that the drive means (38, 39) movesynchronously.
 19. The balance of claim 11, wherein the drive means (38,39) are powered by a single motor (28).
 20. The balance of claim 11,wherein more than one panel is slidable and wherein the slidable panelscan be selectively driven and the selection is between the modes ofdriving an individual panel, all panels together, as well as anysubcombination of panels.
 21. The balance of claim 14, wherein a panel(5, 6, 12) that is coupled to the drive means (38, 39) is set in motionin a desired direction by pushing manually in the desired direction ofmovement against any portion of said panel (5, 6, 12).
 22. The balanceof claim 1, further comprising a carrying handle (13).
 23. The balanceof claim 22, wherein the carrying handle is configured as a rail for aguide element (14) of a guiding device (120) of the top cover panel(12).
 24. The balance of claim 23, wherein the guide element (14)comprises a vertical body (78) holding a vertical gear shaft (66) withan upper gear (73 a) and a lower gear (74 a) and the guiding devicecomprises a pair of gear racks (73, 74) meshing with the gears (73 a, 74a).
 25. The balance of claim 23, wherein the guide element (14) islaterally constrained in the guiding device by one of a glidingconstraint and a rolling constraint, the latter constraint comprisingguide rollers (75, 76).
 26. The balance of claim 1, wherein at least oneof the side-wall panels (5, 6), front-wall panel (7), top-cover panel(12) and rear wall 9 comprises cutout passages (20) for cables andconduits (123).
 27. The balance of claim 26, wherein the cutout passages(20) can be closed by means of clip-on covers (21, 21′, 21″, 113). 28.The balance of claim 27, wherein the cutout passages (20) are providedwith clip-on devices (21″) with equipment holders (130) for tools. 29.The balance of claim 27, comprising side wall panels (114) of differentheight, wherein the cutout passages (20) are provided with clip-ondevices (113) that cooperate with holder rails 115 as part of theguiding device for the slidable side wall panels (114) of differentheight.
 30. The balance of claim 1, comprising an accessory unit (140)containing modules from the group of electric power supplies and controlelectronics.
 31. The balance of claim 30, wherein the stationary part ofthe balances comprises a housing (3) and the accessory unit (140) isintegrated in the housing (3).
 32. The balance of claim 30, wherein theaccessory unit (140) comprises passages (147) for cables and conduits(123).
 33. The balance of claim 32, wherein the accessory unit (140) isconnected to the rear wall (9) through guide channels (143, 143′) forthe conduits and cables (123).
 34. The balance of claim 33, wherein theguide channels (143, 143′) are integrated in the housing (3) and can beclosed to the outside by means of covers.